1. Field of the Invention
The present invention relates to a multi-plate clutch, and more particularly to a multi-plate clutch for a racing car.
2. Description of the Related Art
In general, a multi-plate clutch used in a racing car or the like is provided with a first cylindrical portion that is configured to be attached to a flywheel. A hub flange having a second cylindrical portion is disposed radially inwardly of the first cylindrical portion. The hub flange is connected to a shaft. Drive plates and driven plates are engaged between the first and second cylindrical portions, respectively. A pressure mechanism selectively urges the drive and driven plates toward the flywheel. The pressure mechanism includes a clutch cover, a pressure plate and a diaphragm spring for biasing the pressure plate. The pressure mechanism is fixed to the first cylindrical portion and is provided on a side opposite the drive plates and the driven plates.
In a car race, since a good start may decide a race, the role of clutch, especially in setting a car in motion is significant. The rotational speed of the engine at the start of a race is very high, so that clutch engagement when setting the car in motion is extremely delicate and a driver is usually careful with a clutch operation. Just before the start of a race, the driver waits for a sign which indicates the start of the race while preventing the car from moving and keeps a certain amount of clutch torque in the clutch without fully engaging the clutch until the actual start of the race. Then, the driver releases the brakes, engages the clutch simultaneous with the sign indicating the start of the race, and then the car is put in motion. In this case, it is desirable that there is no change in clutch torque during the clutch in the engaging and dis-engaging process until the car is in motion.
However, when the clutch is in the engaging process for a long time with continued friction producing sliding between plates, the drive plates, driven plates and other members adjacent thereto are heated due to the friction. Thus, these members thermally expand in the axial direction and the pressure load of the diaphragm spring is relatively increased. The thermal expansion can cause abrupt increases in clutch torque even though the driver keeps a generally constant force on the clutch pedal. As a result, the transmitted clutch torque may exceed the amount of torque transmission desired by the driver at critical moments. Consequently, the drive plates and the driven plates undergo unusual wear due to friction. As well, the driver may discover the clutch is more or less fully engaged or dis-engaged than is desired at a critical time.